Integrating biodiversity considerations into urban golf courses: Managers’ perceptions and woody plant diversity in the Eastern Cape, South Africa
- Jarrett, Mitchell, Shackleton, Charlie M
- Authors: Jarrett, Mitchell , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180353 , vital:43356 , xlink:href="https://doi.org/10.1080/1747423X.2017.1325525"
- Description: Rapid rates of urbanisation affect biodiversity through habitat fragmentation and loss. Because urban golf courses are large green spaces, they potentially harbour much biodiversity if managed for such. The area of untransformed land of golf courses in the Eastern Cape (South Africa) was determined using Geographic Information System (GIS), the woody plant composition of a subsample was determined by field sampling and the greenkeepers were interviewed. There was a significant relationship between climate and woody cover, species richness and percentage native plants but not species diversity. There was no relationship between management scores and species richness, diversity and percentage native. Significant relationships were evident between woody plant species richness and course income, number of grounds staff, number of club members and greenkeepers’ years of experience. These results suggest a complex suite of factors that play a role in the woody plant composition of urban golf courses and their contribution to urban biodiversity.
- Full Text:
- Date Issued: 2017
- Authors: Jarrett, Mitchell , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180353 , vital:43356 , xlink:href="https://doi.org/10.1080/1747423X.2017.1325525"
- Description: Rapid rates of urbanisation affect biodiversity through habitat fragmentation and loss. Because urban golf courses are large green spaces, they potentially harbour much biodiversity if managed for such. The area of untransformed land of golf courses in the Eastern Cape (South Africa) was determined using Geographic Information System (GIS), the woody plant composition of a subsample was determined by field sampling and the greenkeepers were interviewed. There was a significant relationship between climate and woody cover, species richness and percentage native plants but not species diversity. There was no relationship between management scores and species richness, diversity and percentage native. Significant relationships were evident between woody plant species richness and course income, number of grounds staff, number of club members and greenkeepers’ years of experience. These results suggest a complex suite of factors that play a role in the woody plant composition of urban golf courses and their contribution to urban biodiversity.
- Full Text:
- Date Issued: 2017
Introduction: Researching sustainable development learning pathways towards progression in learning and work
- Lotz-Sisitka, Heila, Ramsarup, Preesha, Bolton, Heidi
- Authors: Lotz-Sisitka, Heila , Ramsarup, Preesha , Bolton, Heidi
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , bulletin
- Identifier: http://hdl.handle.net/10962/436401 , vital:73269 , ISBN bulletin , https://www.saqa.org.za/wp-content/uploads/2023/02/SAQA-Bulletin-2017-1.pdf#page=37
- Description: Environment and sustainable development issues are increasingly seen as complex, multi-faceted and integral to social and economic development, as can be seen from the recently proclaimed sustainable development goals (www.globalgoals.org1 ). As societies grapple with the rapid and catastrophic effects of environmental degradation, anthropogenic earth system change and a long history of unsustainable development, educa-tional systems have had to attempt to comprehend meaningfully, the im-plications. Within post-apartheid South Africa, these challenges are mark-edly more complex. In a country facing fundamental national transfor-mation on every front, the environment and sustainable development discourses are raising significant new challenges for work and learning systems.
- Full Text:
- Date Issued: 2017
- Authors: Lotz-Sisitka, Heila , Ramsarup, Preesha , Bolton, Heidi
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , bulletin
- Identifier: http://hdl.handle.net/10962/436401 , vital:73269 , ISBN bulletin , https://www.saqa.org.za/wp-content/uploads/2023/02/SAQA-Bulletin-2017-1.pdf#page=37
- Description: Environment and sustainable development issues are increasingly seen as complex, multi-faceted and integral to social and economic development, as can be seen from the recently proclaimed sustainable development goals (www.globalgoals.org1 ). As societies grapple with the rapid and catastrophic effects of environmental degradation, anthropogenic earth system change and a long history of unsustainable development, educa-tional systems have had to attempt to comprehend meaningfully, the im-plications. Within post-apartheid South Africa, these challenges are mark-edly more complex. In a country facing fundamental national transfor-mation on every front, the environment and sustainable development discourses are raising significant new challenges for work and learning systems.
- Full Text:
- Date Issued: 2017
Investigating the effects various compilers have on the electromagnetic signature of a cryptographic executable
- Frieslaar, Ibraheem, Irwin, Barry V W
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430207 , vital:72673 , https://doi.org/10.1145/3129416.3129436
- Description: This research investigates changes in the electromagnetic (EM) signatures of a cryptographic binary executable based on compile-time parameters to the GNU and clang compilers. The source code was compiled and executed on a Raspberry Pi 2, which utilizes the ARMv7 CPU. Various optimization flags are enabled at compile-time and the output of the binary executable's EM signatures are captured at run-time. It is demonstrated that GNU and clang compilers produced different EM signature on program execution. The results indicated while utilizing the O3 optimization flag, the EM signature of the program changes. Additionally, the g++ compiler demonstrated fewer instructions were required to run the executable; this related to fewer EM emissions leaked. The EM data from the various compilers under different optimization levels was used as input data for a correlation power analysis attack. The results indicated that partial AES-128 encryption keys was possible. In addition, the fewest subkeys recovered was when the clang compiler was used with level O2 optimization. Finally, the research was able to recover 15 of 16 AES-128 cryptographic algorithm's subkeys, from the the Pi.
- Full Text:
- Date Issued: 2017
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430207 , vital:72673 , https://doi.org/10.1145/3129416.3129436
- Description: This research investigates changes in the electromagnetic (EM) signatures of a cryptographic binary executable based on compile-time parameters to the GNU and clang compilers. The source code was compiled and executed on a Raspberry Pi 2, which utilizes the ARMv7 CPU. Various optimization flags are enabled at compile-time and the output of the binary executable's EM signatures are captured at run-time. It is demonstrated that GNU and clang compilers produced different EM signature on program execution. The results indicated while utilizing the O3 optimization flag, the EM signature of the program changes. Additionally, the g++ compiler demonstrated fewer instructions were required to run the executable; this related to fewer EM emissions leaked. The EM data from the various compilers under different optimization levels was used as input data for a correlation power analysis attack. The results indicated that partial AES-128 encryption keys was possible. In addition, the fewest subkeys recovered was when the clang compiler was used with level O2 optimization. Finally, the research was able to recover 15 of 16 AES-128 cryptographic algorithm's subkeys, from the the Pi.
- Full Text:
- Date Issued: 2017
Investigating the electromagnetic side channel leakage from a raspberry pi
- Frieslaar, Ibraheem, Irwin, Barry V W
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429548 , vital:72621 , https://ieeexplore.ieee.org/abstract/document/8251771
- Description: This research investigates the Electromagnetic (EM) side channel leakage of a Raspberry Pi 2 B+. An evaluation is performed on the EM leakage as the device executes the AES-128 cryptographic algorithm contained in the Crypto++ library in a threaded environment. Four multi-threaded implementations are evaluated. These implementations are Portable Operating System Interface Threads, C++11 threads, Threading Building Blocks, and OpenMP threads. It is demonstrated that the various thread techniques have distinct variations in frequency and shape as EM emanations is leaked from the Raspberry Pi. Additionally, noise is introduced while the cryptographic algorithm executes. The results indicates that tt is still possible to visibly see the execution of the cryptographic algorithm. However, out of 50 occasions the cryptographic execution was not detected 32 times. It was further identified when calculating prime numbers, the cryptographic algorithm becomes hidden. Furthermore, the analysis pointed in the direction that when high prime numbers are calculated there is a window where the cryptographic algorithm can not be seen visibly in the EM spectrum.
- Full Text:
- Date Issued: 2017
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429548 , vital:72621 , https://ieeexplore.ieee.org/abstract/document/8251771
- Description: This research investigates the Electromagnetic (EM) side channel leakage of a Raspberry Pi 2 B+. An evaluation is performed on the EM leakage as the device executes the AES-128 cryptographic algorithm contained in the Crypto++ library in a threaded environment. Four multi-threaded implementations are evaluated. These implementations are Portable Operating System Interface Threads, C++11 threads, Threading Building Blocks, and OpenMP threads. It is demonstrated that the various thread techniques have distinct variations in frequency and shape as EM emanations is leaked from the Raspberry Pi. Additionally, noise is introduced while the cryptographic algorithm executes. The results indicates that tt is still possible to visibly see the execution of the cryptographic algorithm. However, out of 50 occasions the cryptographic execution was not detected 32 times. It was further identified when calculating prime numbers, the cryptographic algorithm becomes hidden. Furthermore, the analysis pointed in the direction that when high prime numbers are calculated there is a window where the cryptographic algorithm can not be seen visibly in the EM spectrum.
- Full Text:
- Date Issued: 2017
Investigating the utilization of the secure hash algorithm to generate electromagnetic noise
- Frieslaar, Ibraheem, Irwin, Barry V W
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430222 , vital:72674 , https://doi.org/10.1145/3163080.3163089
- Description: This research introduces an electromagnetic (EM) noise generator known as the FRIES noise generator to mitigate and obfuscate Side Channel Analysis (SCA) attacks against a Raspberry Pi. The FRIES noise generator utilizes the implementation of the Secure Hash Algorithm (SHA) from OpenSSL to generate white noise within the EM spectrum. This research further contributes to the body of knowledge by demonstrating that the SHA implementation of libcrypto++ and OpenSSL had different EM signatures. It was further revealed that as a more secure implementation of the SHA was executed additional data lines were used, resulting in increased EM emissions. It was demonstrated that the OpenSSL implementations of the SHA was more optimized as opposed to the libcrypto++ implementation by utilizing less resources and not leaving the device in a bottleneck. The FRIES daemon added noise to the EM leakage which prevents the visual location of the AES-128 cryptographic implementation. Finally, the cross-correlation test demonstrated that the EM features of the AES-128 algorithm was not detected within the FRIES noise.
- Full Text:
- Date Issued: 2017
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430222 , vital:72674 , https://doi.org/10.1145/3163080.3163089
- Description: This research introduces an electromagnetic (EM) noise generator known as the FRIES noise generator to mitigate and obfuscate Side Channel Analysis (SCA) attacks against a Raspberry Pi. The FRIES noise generator utilizes the implementation of the Secure Hash Algorithm (SHA) from OpenSSL to generate white noise within the EM spectrum. This research further contributes to the body of knowledge by demonstrating that the SHA implementation of libcrypto++ and OpenSSL had different EM signatures. It was further revealed that as a more secure implementation of the SHA was executed additional data lines were used, resulting in increased EM emissions. It was demonstrated that the OpenSSL implementations of the SHA was more optimized as opposed to the libcrypto++ implementation by utilizing less resources and not leaving the device in a bottleneck. The FRIES daemon added noise to the EM leakage which prevents the visual location of the AES-128 cryptographic implementation. Finally, the cross-correlation test demonstrated that the EM features of the AES-128 algorithm was not detected within the FRIES noise.
- Full Text:
- Date Issued: 2017
Investigation of photophysicochemical properties of zinc phthalocyanines conjugated to metallic nanoparticles
- Dube, Edith, Nwaji, Njemuwa, Oluwole, David O, Mack, John, Nyokong, Tebello
- Authors: Dube, Edith , Nwaji, Njemuwa , Oluwole, David O , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233425 , vital:50089 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.09.020"
- Description: The syntheses of zinc(II) tetra–[3–(4–phenoxy) (propanoic acid) phthalocyanine] (2) and zinc(II) mono–[3–(4–phenoxy) (propanoic acid) phthalocyanine (3) are reported in this work. Compounds 2 and 3 were covalently linked to glutathione capped silver (AgNPs–GSH), gold (AuNPs–GSH) and silver-gold alloy (Ag3Au1NPs–GSH) nanoparticles (NPs) via an amide bond formation to afford the conjugates: 2–AgNPs–GSH, 3–AgNPs–GSH, 2–AuNPs–GSH, 3–AuNPs–GSH, 2-Ag3Au1NPs–GSH and 3-Ag3Au1NPs–GSH. The photophysicochemical behaviours of the compounds and their conjugates with NPs were assessed in solution. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet quantum yields in comparison to the compounds. Accordingly, the AgNPs and AuNPs conjugates with the compounds afforded high singlet quantum yields. On the contrary, the conjugates of the alloy afforded decreased singlet quantum yields probably due to the screening effect. The compounds and their conjugates with NPs could serve as a viable and efficacious photosensitizer for photodynamic therapy.
- Full Text:
- Date Issued: 2017
- Authors: Dube, Edith , Nwaji, Njemuwa , Oluwole, David O , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233425 , vital:50089 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.09.020"
- Description: The syntheses of zinc(II) tetra–[3–(4–phenoxy) (propanoic acid) phthalocyanine] (2) and zinc(II) mono–[3–(4–phenoxy) (propanoic acid) phthalocyanine (3) are reported in this work. Compounds 2 and 3 were covalently linked to glutathione capped silver (AgNPs–GSH), gold (AuNPs–GSH) and silver-gold alloy (Ag3Au1NPs–GSH) nanoparticles (NPs) via an amide bond formation to afford the conjugates: 2–AgNPs–GSH, 3–AgNPs–GSH, 2–AuNPs–GSH, 3–AuNPs–GSH, 2-Ag3Au1NPs–GSH and 3-Ag3Au1NPs–GSH. The photophysicochemical behaviours of the compounds and their conjugates with NPs were assessed in solution. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet quantum yields in comparison to the compounds. Accordingly, the AgNPs and AuNPs conjugates with the compounds afforded high singlet quantum yields. On the contrary, the conjugates of the alloy afforded decreased singlet quantum yields probably due to the screening effect. The compounds and their conjugates with NPs could serve as a viable and efficacious photosensitizer for photodynamic therapy.
- Full Text:
- Date Issued: 2017
Issues-Based Enquiry: An Enabling Pedagogy for ESD in Teacher Education and School Geography
- Authors: Wilmot, Diana P
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436266 , vital:73253 , ISBN 978-3-319-45989-9 , https://doi.org/10.1007/978-3-319-45989-9_10
- Description: This chapter addresses the need for innovations in geography teacher education programmes in a developing world context. More specifically, it responds to the need for practical ‘how to’ examples for ESD integration into school geography by de-scribing a pedagogical experiment that was piloted with in-service Namibian teachers and education development offic-ers (EDOs) enrolled for a Bachelor of Education (Honours) de-gree in 2014. The theoretical constructs underpinning the ex-periment’s design and pedagogical approach as well as the teacher professional development model are described. This is followed by a description and justification of the methodology used to answer the research question: ‘How can issues-based enquiry enable the integration of ESD at the micro level of the classroom?’ The findings of the experiment provide evidence of how issues-based enquiry, underpinned by active learning and constructivist epistemology and a model of teacher pro-fessional development located in reflexive practice, enabled the teachers to acquire foundational knowledge and pedagog-ical content knowledge for effective integration of ESD into school geography. This chapter may offer other teacher educators some guidelines on how to develop teacher capacity to integrate ESD into their own programmes.
- Full Text:
- Date Issued: 2017
- Authors: Wilmot, Diana P
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436266 , vital:73253 , ISBN 978-3-319-45989-9 , https://doi.org/10.1007/978-3-319-45989-9_10
- Description: This chapter addresses the need for innovations in geography teacher education programmes in a developing world context. More specifically, it responds to the need for practical ‘how to’ examples for ESD integration into school geography by de-scribing a pedagogical experiment that was piloted with in-service Namibian teachers and education development offic-ers (EDOs) enrolled for a Bachelor of Education (Honours) de-gree in 2014. The theoretical constructs underpinning the ex-periment’s design and pedagogical approach as well as the teacher professional development model are described. This is followed by a description and justification of the methodology used to answer the research question: ‘How can issues-based enquiry enable the integration of ESD at the micro level of the classroom?’ The findings of the experiment provide evidence of how issues-based enquiry, underpinned by active learning and constructivist epistemology and a model of teacher pro-fessional development located in reflexive practice, enabled the teachers to acquire foundational knowledge and pedagog-ical content knowledge for effective integration of ESD into school geography. This chapter may offer other teacher educators some guidelines on how to develop teacher capacity to integrate ESD into their own programmes.
- Full Text:
- Date Issued: 2017
Laser induced photodegradation of Orange G using phthalocyanine–cobalt ferrite magnetic nanoparticle conjugates electrospun in polystyrene nanofibers
- Mapukata, Sivuyisiwe, Chindeka, Francis, Sekhosana, Kutloano E, Nyokong, Tebello
- Authors: Mapukata, Sivuyisiwe , Chindeka, Francis , Sekhosana, Kutloano E , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188617 , vital:44769 , xlink:href="https://doi.org/10.1016/j.mcat.2017.06.028"
- Description: Conjugates of zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc) and zinc tetraaminophenoxy phthalocyanine (ZnTAPPc) with amine and carboxyl functionalised cobalt ferrite magnetic nanoparticles (CoFe2O4 MNPs), respectively were electrospun into polystyrene (PS) fibers. The resulting composites; ZnTCPPc-CoFe2O4/PS and ZnTAPPc-CoFe2O4/PS were compared based on their photophysical properties and photocatalytic efficiencies in degrading Orange G (OG) using laser as the photoexcitation source. The photocatalytic efficiencies of ZnTCPPc-CoFe2O4/PS and ZnTAPPc-CoFe2O4/PS were compared based on them having different lengths in the linkage chains between the Pcs and CoFe2O4 MNPs and different sizes. Covalent linkage of the Pcs to the CoFe2O4 MNPs enhanced the singlet oxygen and reactive oxygen species (ROS) production of the Pcs and CoFe2O4, respectively hence ZnTCPPc-CoFe2O4/PS and ZnTAPPc-CoFe2O4/PS were found to be more effective photocatalysts than their respective Pcs and CoFe2O4 MNPs. Moreover, the kinetic analyses of the photodecomposition of OG showed that the degradation was in agreement with both pseudo-first order kinetics and followed the Langmuir–Hinshelwood model.
- Full Text:
- Date Issued: 2017
- Authors: Mapukata, Sivuyisiwe , Chindeka, Francis , Sekhosana, Kutloano E , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188617 , vital:44769 , xlink:href="https://doi.org/10.1016/j.mcat.2017.06.028"
- Description: Conjugates of zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc) and zinc tetraaminophenoxy phthalocyanine (ZnTAPPc) with amine and carboxyl functionalised cobalt ferrite magnetic nanoparticles (CoFe2O4 MNPs), respectively were electrospun into polystyrene (PS) fibers. The resulting composites; ZnTCPPc-CoFe2O4/PS and ZnTAPPc-CoFe2O4/PS were compared based on their photophysical properties and photocatalytic efficiencies in degrading Orange G (OG) using laser as the photoexcitation source. The photocatalytic efficiencies of ZnTCPPc-CoFe2O4/PS and ZnTAPPc-CoFe2O4/PS were compared based on them having different lengths in the linkage chains between the Pcs and CoFe2O4 MNPs and different sizes. Covalent linkage of the Pcs to the CoFe2O4 MNPs enhanced the singlet oxygen and reactive oxygen species (ROS) production of the Pcs and CoFe2O4, respectively hence ZnTCPPc-CoFe2O4/PS and ZnTAPPc-CoFe2O4/PS were found to be more effective photocatalysts than their respective Pcs and CoFe2O4 MNPs. Moreover, the kinetic analyses of the photodecomposition of OG showed that the degradation was in agreement with both pseudo-first order kinetics and followed the Langmuir–Hinshelwood model.
- Full Text:
- Date Issued: 2017
Learning pathways and articulation: Early conceptual explorations and implications for research design (s)
- Lotz-Sisitka, Heila, Ramsarup, Preesha
- Authors: Lotz-Sisitka, Heila , Ramsarup, Preesha
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , bulletin
- Identifier: http://hdl.handle.net/10962/436388 , vital:73268 , ISBN bulletin , https://www.saqa.org.za/wp-content/uploads/2023/02/SAQA-Bulletin-2017-1.pdf#page=37
- Description: This paper is an introductory, exploratory paper which opened up the ter-rain for a second phase of the South African Qualifications Authority (SAQA)-Rhodes University research partnership focusing on change-oriented workplace learning and sustainability practices, with an emphasis on learning pathways (the main period being 2011-2013, ongoing until 2016). The paper reviews early conceptual explorations of learning path-ways and articulation questions, as these relate to a transversal issue8 in the National Qualifications Framework (NQF), namely environment and sustainable development.
- Full Text:
- Date Issued: 2017
- Authors: Lotz-Sisitka, Heila , Ramsarup, Preesha
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , bulletin
- Identifier: http://hdl.handle.net/10962/436388 , vital:73268 , ISBN bulletin , https://www.saqa.org.za/wp-content/uploads/2023/02/SAQA-Bulletin-2017-1.pdf#page=37
- Description: This paper is an introductory, exploratory paper which opened up the ter-rain for a second phase of the South African Qualifications Authority (SAQA)-Rhodes University research partnership focusing on change-oriented workplace learning and sustainability practices, with an emphasis on learning pathways (the main period being 2011-2013, ongoing until 2016). The paper reviews early conceptual explorations of learning path-ways and articulation questions, as these relate to a transversal issue8 in the National Qualifications Framework (NQF), namely environment and sustainable development.
- Full Text:
- Date Issued: 2017
Local knowledge on the uses, habitat, and change in abundance of multipurpose mimusops species in Benin
- Sinasson Gisèle K, Shackleton, Charlie M, Assogbadjo, Achille E, Sinsin, Brice
- Authors: Sinasson Gisèle K , Shackleton, Charlie M , Assogbadjo, Achille E , Sinsin, Brice
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181105 , vital:43699 , xlink:href="https://doi.org/10.1007/s12231-017-9370-6"
- Description: Multipurpose NTFP species typically experience higher harvest demand because of their multiple uses, which, when combined with unsustainable land use practices, may threaten population viability. We assessed local knowledge on the uses, habitat, and population status of Mimusops andongensis and Mimusops kummel, both multipurpose NTFP species in Benin, to promote their valorization and conservation and thus sustain local knowledge on their uses for domestication issues. One hundred households were randomly selected for structured interviews for M. andongensis and 500 for M. kummel. The relationship between age, sex, and ethnic groups and the species uses was assessed using comparison and correspondence analyses. Nearly all organs of the species were used. Both species were mainly exploited for medicinal purposes but also in construction and as firewood. We found similarities in some uses of the species organs, although the species occur in different ecological zones and are used by different ethnic groups. This result should be considered for the valorization of the species. Most informants reported that populations of M. andongensis were decreasing, although some felt that they were increasing, whereas less than one-third said that M. kummel was decreasing. There were strong relationships between gender, age, and ethnic affiliation of the users and the exploited organs of both species. Potential uses exist based on both the past and current uses of the species and in comparison to other countries where they are exploited. Local ethnoecological knowledge and practices will help to valorize and conserve the species. However, further research on the species’ seed germination and propagation ability are also necessary.
- Full Text:
- Date Issued: 2017
- Authors: Sinasson Gisèle K , Shackleton, Charlie M , Assogbadjo, Achille E , Sinsin, Brice
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181105 , vital:43699 , xlink:href="https://doi.org/10.1007/s12231-017-9370-6"
- Description: Multipurpose NTFP species typically experience higher harvest demand because of their multiple uses, which, when combined with unsustainable land use practices, may threaten population viability. We assessed local knowledge on the uses, habitat, and population status of Mimusops andongensis and Mimusops kummel, both multipurpose NTFP species in Benin, to promote their valorization and conservation and thus sustain local knowledge on their uses for domestication issues. One hundred households were randomly selected for structured interviews for M. andongensis and 500 for M. kummel. The relationship between age, sex, and ethnic groups and the species uses was assessed using comparison and correspondence analyses. Nearly all organs of the species were used. Both species were mainly exploited for medicinal purposes but also in construction and as firewood. We found similarities in some uses of the species organs, although the species occur in different ecological zones and are used by different ethnic groups. This result should be considered for the valorization of the species. Most informants reported that populations of M. andongensis were decreasing, although some felt that they were increasing, whereas less than one-third said that M. kummel was decreasing. There were strong relationships between gender, age, and ethnic affiliation of the users and the exploited organs of both species. Potential uses exist based on both the past and current uses of the species and in comparison to other countries where they are exploited. Local ethnoecological knowledge and practices will help to valorize and conserve the species. However, further research on the species’ seed germination and propagation ability are also necessary.
- Full Text:
- Date Issued: 2017
Modelling dialectical processes in environmental learning
- Authors: Schudel, Ingrid J
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/294409 , vital:57219 , xlink:href="https://doi.org/10.1080/14767430.2017.1288061"
- Description: This paper describes a critical realist intensive case study, which develops and tests a ‘dialectic process model of transformative learning’. The model is inspired by Bhaskar's (1993) onto-axiological chain (or MELD Schema) as outlined in his formulation of dialectical critical realism. The study describes transformative environmental learning processes focusing on food security in two primary schools in rural South Africa. The model elaborates on the four links in the onto-axiological chain by describing four knowledge interests across the two cases: knowledge of ‘what is and what is not’, knowledge of ‘what could be’, knowledge of ‘what should be’, and knowledge of ‘what can be’. The model also highlights the emergent nature of epistemic relations in transformative learning processes. The paper discusses the model in relation to a transformative, open-ended and context specific approach to Environmental Education (EE)/ESD. The paper illustrates that Bhaskar’s MELD is a robust schema for investigating learning-led change in EE and suggests its relevance in other research contexts concerned with societal transformation.
- Full Text:
- Date Issued: 2017
- Authors: Schudel, Ingrid J
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/294409 , vital:57219 , xlink:href="https://doi.org/10.1080/14767430.2017.1288061"
- Description: This paper describes a critical realist intensive case study, which develops and tests a ‘dialectic process model of transformative learning’. The model is inspired by Bhaskar's (1993) onto-axiological chain (or MELD Schema) as outlined in his formulation of dialectical critical realism. The study describes transformative environmental learning processes focusing on food security in two primary schools in rural South Africa. The model elaborates on the four links in the onto-axiological chain by describing four knowledge interests across the two cases: knowledge of ‘what is and what is not’, knowledge of ‘what could be’, knowledge of ‘what should be’, and knowledge of ‘what can be’. The model also highlights the emergent nature of epistemic relations in transformative learning processes. The paper discusses the model in relation to a transformative, open-ended and context specific approach to Environmental Education (EE)/ESD. The paper illustrates that Bhaskar’s MELD is a robust schema for investigating learning-led change in EE and suggests its relevance in other research contexts concerned with societal transformation.
- Full Text:
- Date Issued: 2017
More is not necessarily better: the interaction between insect population density and culture age of fungus on the control of invasive weed water hyacinth
- Authors: Ray, Puja , Hill, Martin P
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424777 , vital:72183 , xlink:href="https://doi.org/10.1007/s10750-015-2454-3"
- Description: The possibilities of a positive or negative impact the biocontrol agents may have on each other as well as on the control of the weed itself, inspired us to study the interactions between the mirid, Eccritotarsus catarinensis and the phytopathogen, Acremonium zonatum, biocontrol agents of water hyacinth, Eichhornia crassipes. Observations were made on disease initiation time of A. zonatum grown for different time durations with different insect densities on water hyacinth. In absence of mirids, the lowest (3.1 days) and the highest (5.1 days) disease initiation time was observed using 21 and 42 days old culture respectively. In treatments involving mirids, the shortest (1.78 days) and the longest (13.22 days) disease initiation time by A. zonatum was observed on water hyacinth with 10 and 20 mirids/plant respectively. By the 30th day, maximum percentage damage (77.9%) was observed in the treatment of 21 day old fungal culture with 20 mirid density/plant despite of initial delay in disease initiation. This result suggests an initial development of a plant defense response due to mirid feeding delaying the pathogen from establishing. Extensive studies involving multitrophic interactions should be an essential part of pre-release assessments to enhance the success rates of biological control of weeds.
- Full Text:
- Date Issued: 2017
- Authors: Ray, Puja , Hill, Martin P
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424777 , vital:72183 , xlink:href="https://doi.org/10.1007/s10750-015-2454-3"
- Description: The possibilities of a positive or negative impact the biocontrol agents may have on each other as well as on the control of the weed itself, inspired us to study the interactions between the mirid, Eccritotarsus catarinensis and the phytopathogen, Acremonium zonatum, biocontrol agents of water hyacinth, Eichhornia crassipes. Observations were made on disease initiation time of A. zonatum grown for different time durations with different insect densities on water hyacinth. In absence of mirids, the lowest (3.1 days) and the highest (5.1 days) disease initiation time was observed using 21 and 42 days old culture respectively. In treatments involving mirids, the shortest (1.78 days) and the longest (13.22 days) disease initiation time by A. zonatum was observed on water hyacinth with 10 and 20 mirids/plant respectively. By the 30th day, maximum percentage damage (77.9%) was observed in the treatment of 21 day old fungal culture with 20 mirid density/plant despite of initial delay in disease initiation. This result suggests an initial development of a plant defense response due to mirid feeding delaying the pathogen from establishing. Extensive studies involving multitrophic interactions should be an essential part of pre-release assessments to enhance the success rates of biological control of weeds.
- Full Text:
- Date Issued: 2017
Multiple drivers of local (non-) compliance in community-based marine resource management: Case studies from the South Pacific
- Rohe, Janne R, Aswani, Shankar, Schlüter, Achim, Ferse, Sebastian
- Authors: Rohe, Janne R , Aswani, Shankar , Schlüter, Achim , Ferse, Sebastian
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/420445 , vital:71744 , xlink:href="https://doi.org/10.3389/fmars.2017.00172"
- Description: The outcomes of marine conservation and related management interventions depend to a large extent on people's compliance with these rule systems. In the South Pacific, community-based marine resource management (CBMRM) has gained wide recognition as a strategy for the sustainable management of marine resources. In current practice, CBMRM initiatives often build upon customary forms of marine governance, integrating scientific advice and management principles in collaboration with external partners. However, diverse socio-economic developments as well as limited legal mandates can challenge these approaches. Compliance with and effective (legally-backed) enforcement of local management strategies constitute a growing challenge for communities—often resulting in considerable impact on the success or failure of CBMRM. Marine management arrangements are highly dynamic over time, and similarly compliance with rule systems tends to change depending on context. Understanding the factors contributing to (non-) compliance in a given setting is key to the design and function of adaptive management approaches. Yet, few empirical studies have looked in depth into the dynamics around local (non-) compliance with local marine tenure rules under the transforming management arrangements. Using two case studies from Solomon Islands and Fiji, we investigate what drives local (non-) compliance with CBMRM and what hinders or supports its effective enforcement. The case studies reveal that non-compliance is mainly driven by: (1) diminishing perceived legitimacy of local rules and rule-makers; (2) increased incentives to break rules due to market access and/ or lack of alternative income; and (3) relatively weak enforcement of local rules (i.e., low perceptions of risk from sanctions for rule-breaking). These drivers do not stand alone but can act together and add up to impair effective management. We further analyze how enforcement of CBMRM is challenged through a range of institutional; socio-cultural and technical/financial constraints, which are in parts a result of the dynamism and ongoing transformations of management arrangements. Our study underlines the importance of better understanding and contextualizing marine resource management processes under dynamic conditions for an improved understanding of compliance in a particular setting.
- Full Text:
- Date Issued: 2017
- Authors: Rohe, Janne R , Aswani, Shankar , Schlüter, Achim , Ferse, Sebastian
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/420445 , vital:71744 , xlink:href="https://doi.org/10.3389/fmars.2017.00172"
- Description: The outcomes of marine conservation and related management interventions depend to a large extent on people's compliance with these rule systems. In the South Pacific, community-based marine resource management (CBMRM) has gained wide recognition as a strategy for the sustainable management of marine resources. In current practice, CBMRM initiatives often build upon customary forms of marine governance, integrating scientific advice and management principles in collaboration with external partners. However, diverse socio-economic developments as well as limited legal mandates can challenge these approaches. Compliance with and effective (legally-backed) enforcement of local management strategies constitute a growing challenge for communities—often resulting in considerable impact on the success or failure of CBMRM. Marine management arrangements are highly dynamic over time, and similarly compliance with rule systems tends to change depending on context. Understanding the factors contributing to (non-) compliance in a given setting is key to the design and function of adaptive management approaches. Yet, few empirical studies have looked in depth into the dynamics around local (non-) compliance with local marine tenure rules under the transforming management arrangements. Using two case studies from Solomon Islands and Fiji, we investigate what drives local (non-) compliance with CBMRM and what hinders or supports its effective enforcement. The case studies reveal that non-compliance is mainly driven by: (1) diminishing perceived legitimacy of local rules and rule-makers; (2) increased incentives to break rules due to market access and/ or lack of alternative income; and (3) relatively weak enforcement of local rules (i.e., low perceptions of risk from sanctions for rule-breaking). These drivers do not stand alone but can act together and add up to impair effective management. We further analyze how enforcement of CBMRM is challenged through a range of institutional; socio-cultural and technical/financial constraints, which are in parts a result of the dynamism and ongoing transformations of management arrangements. Our study underlines the importance of better understanding and contextualizing marine resource management processes under dynamic conditions for an improved understanding of compliance in a particular setting.
- Full Text:
- Date Issued: 2017
Nanocomposites of sulphur-nitrogen co-doped graphene oxide nanosheets and cobalt mono carboxyphenoxy phthalocyanines for facile electrocatalysis
- Shumba, Munyaradzi, Centane, Sixolile, Chindeka, Francis, Nyokong, Tebello
- Authors: Shumba, Munyaradzi , Centane, Sixolile , Chindeka, Francis , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239665 , vital:50753 , xlink:href="https://doi.org/10.1016/j.jelechem.2017.03.006"
- Description: Nanocomposites consisting of cobalt mono carboxyphenoxy phthalocyanine (CoMCPhPc) either covalently linked to graphene oxide nanosheets (GONS), sulphur doped graphene oxide nanosheets (SDGONS), nitrogen doped graphene oxide nanosheets (NDGONS) or sulphur/nitrogen co-doped graphene oxide nanosheets (SNDGONS) or sequentially added were used to modify glassy carbon electrode. The modified electrodes were characterised using several techniques: voltammetry, X-ray photon spectroscopy and scanning electron spectroscopy before testing their activity on the detection of hydrogen peroxide at pH 7. The presence of SNDGONS had a significant improvement on the currents as compared to CoMCPhPc modification alone in both sequentially added or covalently linked to MPcs. CoMCPhPc-SNDGONS(seq)-GCE and CoMCPhPc-SDGONS(linked)-GCE resulted in impressive limits of detection and catalytic rate constant values of 1.58 nM and 5.44 nM, 3.07 × 105 M−1 s−1 and 3.01 × 103 M−1 s−1 respectively. Gibbs energy value was determined to be −21.22 kJ mol−1 for CoMCPhPc-SNDGONS(linked)-GCE indicative of a facile spontaneous electroreduction reaction on the surface of this electrode.
- Full Text:
- Date Issued: 2017
- Authors: Shumba, Munyaradzi , Centane, Sixolile , Chindeka, Francis , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239665 , vital:50753 , xlink:href="https://doi.org/10.1016/j.jelechem.2017.03.006"
- Description: Nanocomposites consisting of cobalt mono carboxyphenoxy phthalocyanine (CoMCPhPc) either covalently linked to graphene oxide nanosheets (GONS), sulphur doped graphene oxide nanosheets (SDGONS), nitrogen doped graphene oxide nanosheets (NDGONS) or sulphur/nitrogen co-doped graphene oxide nanosheets (SNDGONS) or sequentially added were used to modify glassy carbon electrode. The modified electrodes were characterised using several techniques: voltammetry, X-ray photon spectroscopy and scanning electron spectroscopy before testing their activity on the detection of hydrogen peroxide at pH 7. The presence of SNDGONS had a significant improvement on the currents as compared to CoMCPhPc modification alone in both sequentially added or covalently linked to MPcs. CoMCPhPc-SNDGONS(seq)-GCE and CoMCPhPc-SDGONS(linked)-GCE resulted in impressive limits of detection and catalytic rate constant values of 1.58 nM and 5.44 nM, 3.07 × 105 M−1 s−1 and 3.01 × 103 M−1 s−1 respectively. Gibbs energy value was determined to be −21.22 kJ mol−1 for CoMCPhPc-SNDGONS(linked)-GCE indicative of a facile spontaneous electroreduction reaction on the surface of this electrode.
- Full Text:
- Date Issued: 2017
Nanosecond optical nonlinearities in low symmetry phthalocyanine nanoconjugates studied using the Z-scan technique
- Nwaji, Njemuwa, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188172 , vital:44729 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.08.053"
- Description: In this study, the photophysical, and nonlinear optical limiting properties of low symmetry tris[(4-benzo[d] thiazol-2-ylphenoxy)-2-phenoxyl acetic acid phthalocyaninato] zinc (II) (3) conjugated to metallic nanoparticles have been investigated using open aperture Z-scan techniques at 532 nm. The nonlinear optical response demonstrated that the studied complex and the nanoconjugates exhibits higher excited state absorption cross-section resulting from S1 and T1 compared to ground state absorption. Enhanced optical limiting performance was observed when the complex was conjugated to nanoparticles with 3SA-AuNPs showing the best optical limiting threshold of 0.39 J/cm2.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188172 , vital:44729 , xlink:href="https://doi.org/10.1016/j.jlumin.2017.08.053"
- Description: In this study, the photophysical, and nonlinear optical limiting properties of low symmetry tris[(4-benzo[d] thiazol-2-ylphenoxy)-2-phenoxyl acetic acid phthalocyaninato] zinc (II) (3) conjugated to metallic nanoparticles have been investigated using open aperture Z-scan techniques at 532 nm. The nonlinear optical response demonstrated that the studied complex and the nanoconjugates exhibits higher excited state absorption cross-section resulting from S1 and T1 compared to ground state absorption. Enhanced optical limiting performance was observed when the complex was conjugated to nanoparticles with 3SA-AuNPs showing the best optical limiting threshold of 0.39 J/cm2.
- Full Text:
- Date Issued: 2017
Nonlinear interactions of zinc phthalocyanine-graphene quantum dots nanocomposites: Investigation of effects of surface functionalization with heteroatoms
- Bankole, Owolabi M, Achadu, Ojodomo J, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Achadu, Ojodomo J , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188474 , vital:44757 , xlink:href="https://doi.org/10.1007/s10895-016-2008-8"
- Description: This study reports the development of functional optical limiting materials composed of pristine graphene (GQDs), nitrogen-doped (NGQDs) and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots covalently linked to mono-amino substituted zinc phthalocyanine (Pc). Open aperture Z-scan technique was employed to monitor the behaviour of the conjugates under tightly focussed Gaussian laser beam using a mode-locked Nd:YAG laser delivering 10 nanosecond (FWHM) pulses at 532 nm wavelength. Nonlinear effect due to reverse saturable absorption was the predominant mechanism; and was attributed to the moderately enhanced triplet population. The major factor(s) responsible for the enhanced nonlinearities in the Pc-NGQDs and Pc-SNGQDs was fully described and attributed to the surface defects caused by the presence of heteroatoms of N and S.
- Full Text:
- Date Issued: 2017
- Authors: Bankole, Owolabi M , Achadu, Ojodomo J , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188474 , vital:44757 , xlink:href="https://doi.org/10.1007/s10895-016-2008-8"
- Description: This study reports the development of functional optical limiting materials composed of pristine graphene (GQDs), nitrogen-doped (NGQDs) and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots covalently linked to mono-amino substituted zinc phthalocyanine (Pc). Open aperture Z-scan technique was employed to monitor the behaviour of the conjugates under tightly focussed Gaussian laser beam using a mode-locked Nd:YAG laser delivering 10 nanosecond (FWHM) pulses at 532 nm wavelength. Nonlinear effect due to reverse saturable absorption was the predominant mechanism; and was attributed to the moderately enhanced triplet population. The major factor(s) responsible for the enhanced nonlinearities in the Pc-NGQDs and Pc-SNGQDs was fully described and attributed to the surface defects caused by the presence of heteroatoms of N and S.
- Full Text:
- Date Issued: 2017
Nonlinear optical dynamics of benzothiazole derivatized phthalocyanines in solution, thin films and when conjugated to nanoparticles
- Nwaji, Njemuwa, Jones, Benjamin, Mack, John, Oluwole, David O, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Jones, Benjamin , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Jones, Benjamin , Mack, John , Oluwole, David O , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190426 , vital:44993 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.05.042"
- Description: Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.
- Full Text:
- Date Issued: 2017
Optical limiters with improved performance based on nanoconjugates of thiol substituted phthalocyanine with CdSe quantum dots and Ag nanoparticles
- Oluwole, David O, Yagodin, Alexey V, Britton, Jonathan, Martynov, Alexander G, Gorbunova, Yulia G, Tsivadze, Aslan Yu, Nyokong, Tebello
- Authors: Oluwole, David O , Yagodin, Alexey V , Britton, Jonathan , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238286 , vital:50605 , xlink:href="https://doi.org/10.1039/C7DT03867D"
- Description: Two alternative synthetic approaches affording a low-symmetry A3B-type phthalocyanine 1 bearing two [2′-(2′′-mercaptoethoxy)ethoxy] anchoring substituents were developed. Due to the presence of thiol groups, this phthalocyanine could be conjugated with TOPO-capped (TOPO - trioctylphosphine)-capped CdSe quantum dots (CdSe-QDs) or oleylamine capped silver nanoparticles (Ag-NPs). The nonlinear optical behaviour of starting phthalocyanine, quantum dots, nanoparticles and their conjugates was studied by using an open aperture Z-scan technique, revealing that the grafting of 1 onto the nanomaterials resulted in a significant enhancement of the optical limiting of 1-Ag and 1-CdSe in comparison with the individual components. The conjugate 1-CdSe, being the first example of Pc-based thiol conjugated with quantum dots, revealed superior limiting characteristics with a limiting threshold below 0.18 J cm−2.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Yagodin, Alexey V , Britton, Jonathan , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238286 , vital:50605 , xlink:href="https://doi.org/10.1039/C7DT03867D"
- Description: Two alternative synthetic approaches affording a low-symmetry A3B-type phthalocyanine 1 bearing two [2′-(2′′-mercaptoethoxy)ethoxy] anchoring substituents were developed. Due to the presence of thiol groups, this phthalocyanine could be conjugated with TOPO-capped (TOPO - trioctylphosphine)-capped CdSe quantum dots (CdSe-QDs) or oleylamine capped silver nanoparticles (Ag-NPs). The nonlinear optical behaviour of starting phthalocyanine, quantum dots, nanoparticles and their conjugates was studied by using an open aperture Z-scan technique, revealing that the grafting of 1 onto the nanomaterials resulted in a significant enhancement of the optical limiting of 1-Ag and 1-CdSe in comparison with the individual components. The conjugate 1-CdSe, being the first example of Pc-based thiol conjugated with quantum dots, revealed superior limiting characteristics with a limiting threshold below 0.18 J cm−2.
- Full Text:
- Date Issued: 2017
Optical limiting properties of 2, 6-dibromo-3, 5-distyrylBODIPY dyes at 532 nm
- Kubheka, Gugu, Mack, John, Kobayashi, Nagao, Kimura, Mitsumi, Nyokong, Tebello
- Authors: Kubheka, Gugu , Mack, John , Kobayashi, Nagao , Kimura, Mitsumi , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190405 , vital:44991 , xlink:href="https://doi.org/10.1142/S1088424617500511"
- Description: Optical limiting properties of 2,6-dibromo-3,5-distyrylBODIPY dyes were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. A strong reverse saturable absorption response was observed even in solution, which suggests that compounds of this type are potentially suitable for use in optical limiting applications.
- Full Text:
- Date Issued: 2017
- Authors: Kubheka, Gugu , Mack, John , Kobayashi, Nagao , Kimura, Mitsumi , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190405 , vital:44991 , xlink:href="https://doi.org/10.1142/S1088424617500511"
- Description: Optical limiting properties of 2,6-dibromo-3,5-distyrylBODIPY dyes were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range. A strong reverse saturable absorption response was observed even in solution, which suggests that compounds of this type are potentially suitable for use in optical limiting applications.
- Full Text:
- Date Issued: 2017
Optical limiting properties of 3, 5-diphenyldibenzo-azaBODIPY at 532 nm
- Kubheka, Gugu, Achadu, Ojodomo J, Mack, John, Nyokong, Tebello
- Authors: Kubheka, Gugu , Achadu, Ojodomo J , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232761 , vital:50022 , xlink:href="https://doi.org/10.1039/C7NJ01503H"
- Description: Optical limiting properties of 3,5-diphenyldibenzo-azaBODIPY were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range and a strong reverse saturable absorption (RSA) response was observed, which can be readily attributed to a two-photon absorption (TPA) assisted excited state absorption (ESA) mechanism in the singlet manifold based on a consideration of the other photophysical properties. The effect of solvent and incorporation into polymer thin films has been investigated in depth. The results indicate that the selection of solvents that enhance the population of the S1 excited state on the nanosecond timescale or embedding the azaBODIPY dye into polymer thin films significantly improves the optical limiting properties.
- Full Text:
- Date Issued: 2017
- Authors: Kubheka, Gugu , Achadu, Ojodomo J , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232761 , vital:50022 , xlink:href="https://doi.org/10.1039/C7NJ01503H"
- Description: Optical limiting properties of 3,5-diphenyldibenzo-azaBODIPY were investigated by using the z-scan technique at 532 nm in the nanosecond pulse range and a strong reverse saturable absorption (RSA) response was observed, which can be readily attributed to a two-photon absorption (TPA) assisted excited state absorption (ESA) mechanism in the singlet manifold based on a consideration of the other photophysical properties. The effect of solvent and incorporation into polymer thin films has been investigated in depth. The results indicate that the selection of solvents that enhance the population of the S1 excited state on the nanosecond timescale or embedding the azaBODIPY dye into polymer thin films significantly improves the optical limiting properties.
- Full Text:
- Date Issued: 2017